The present invention relates to a locking device wherein a trigger bolt for fastening a dead bolt is provided in said dead bolt and can be released by actuating a cooperating assembly placed in a door frame from remote control room.
Conventional locking devices were provided only with dead bolts that were movable forward and backwards by means of thumb-turns operable from the outside and the inside. In the prior art it was not possible that a dead bolt could be locked and unlocked from the outside by turning an outside thumb-turn only, unless a key were used.
The above-mentioned conventional lock devices had the drawback that it was impossible to lock and release a dead bolt from the outside of a door by means of, for example, only a thumb-turn without the use of a key and a cylinder lock. The addition of a cylinder lock makes the locking device larger in size and higher in cost.
The present invention was made to solve the above-mentioned problem and therefore to provide a lock device wherein the dead bolt of the locking mechanism placed in a door can be locked from the outside and the inside respectively by means of corresponding thumb-turns and also can be unlocked even from the outside by means of only the outer thumb-turn by remotely unlocking the dead bolt from the door frame side.